Inhibition of <b><i>Streptococcus mutan</i></b>s Growth and Biofilm Formation by Probiotics in vitro

Abstract

To exert anticaries effects, probiotics are described to inhibit growth and biofilm formation of cariogenic bacteria such as Streptococcus mutans (SM). We screened 8 probiotics and assessed how SM growth or biofilm formation inhibition affects cariogenicity of probiotic-SM mixed-species biofilms in vitro. Growth inhibition was assessed by cocultivating probiotics and 2 SM strains (ATCC 20532/25175) on agar. Probiotics were either precultured before SM cultivation (exclusion), or SM precultured prior to probiotic cultivation (displacement). Inhibition of SM culture growth was assessed visually. Inhibition of SM biofilm formation on bovine enamel was assessed using a continuous-flow short-term biofilm model, again in exclusion or displacement mode. The cariogenicity of mixed-species biofilms of SM with the most promising growth and biofilm formation inhibiting probiotic strains was assessed using an artificial mouth model, and enamel mineral loss (ΔZ) was measured microradiographically. We found limited differences in SM growth inhibition in exclusion versus displacement mode, and in inhibition of SM 20532 versus 25175. Results were therefore pooled. Lactobacillus acidophilus LA-5 inhibited significantly more SM culture growth than most other probiotics. L. casei LC-11 inhibited SM biofilm formation similarly to other alternatives but showed the highest retention of probiotics in the biofilms (p < 0.05). Mineral loss from SM monospecies biofilms (ΔZ = 9,772, 25th/75th percentiles: 6,277/13,558 vol% × µm) was significantly lower than from mixed-species SM × LA-5 biofilms (ΔZ = 24,578, 25th/75th percentiles: 19,081/28,768 vol% × µm; p < 0.01) but significantly higher than from SM × LC-11 biofilms (ΔZ = 4,835, 25th/75th percentiles: 263/7,865 vol% × µm; p < 0.05). Probiotics inhibiting SM culture growth do not necessarily reduce the cariogenicity of SM-probiotic biofilms. Nevertheless, SM biofilm formation inhibition may be relevant in the reduction of cariogenicity.

In vitro beneficial effects of Streptococcus dentisani as potential oral probiotic for periodontal diseases

“…1,31 The most common probiotics strains used in oral health belong to the genera Bifidobacterium and Lactobacillus. 20,30,[32][33][34] For instance, when incorporated to commercial toothpastes, L. casei and L. acidophilus were able to in vitro inhibit Candida albicans and Streptococcus salivarius growth. 33 Recently, it has been hypothesized that oral commensals associated with health are likely to be more effective as probiotic species than the traditional gut-associated probiotic species in terms of ability to colonization, health-promoting functions, biocompatibility, and prophylactic dosage.…”

Ecological Approaches to Dental Caries Prevention: Paradigm Shift or Shibboleth?

“…The local anticaries effects may include competitive inhibition with cariogenic bacteria for nutrition or adhesive surfaces [Terai et al, 2015], selective co-aggregation of MS without disturbing other oral flora Lang et al, 2010], and bacteriocin-producing probiotics targeting MS [Burton et al, 2013]. The most commonly used and studied probiotics belong to the Lactobacillus and Bifidobacterium bacterial genera, although not all their strains have the same efficacy in the inhibition of S. mutans growth or biofilm formation [Schwendicke et al, 2017].…”

“…One of the problems identified in using probiotics for caries prevention is that the commonly available Lactobacillus and Bifidobacterium probiotic bacteria are themselves acidogenic and aciduric, and could contribute to the caries process if such bacteria are allowed to colonize the oral cavity [Maltz and Beighton, 2012]. Recent in vitro biofilm studies have confirmed this apprehension with different strains such as Lactobacillus salivarius W24 [Pham et al, 2009], Lactobacillus rhamnosus GG [Schwendicke et al, 2014a], Bifidobacteria animalis lactis BB12 [Schwendicke et al, 2014b], Lactobacillus rhamnosus LB21 [Fernández et al, 2015], and Lactobacillus acidophilus LA-5 [Schwendicke et al, 2017] which have all been shown to lower biofilm pH. In fact, some Lactobacillus and Bifidobacterium strains have greater cariogenic attributes than even MS [Beighton et al, 2010].…”

Application of Antibiotics/Antimicrobial Agents on Dental Caries

“…For example, S. salivarius strains can produce bacteriocin-like inhibitory substances with a broad spectrum of activity against cariogenic streptococci including S. mutans. S. oligofermentans is a bacterium that appears to be inversely correlated with the presence of S. mutans within dental plaque samples and was shown to produce hydrogen peroxide with lactic acid as the substrate, leading to the inhibition of S. mutans growth [112,113].…”